Function subscribe

src/ink/components/ClockContext.tsx:41–48

(onChange, keepAlive)

  }
  return {
    subscribe(onChange, keepAlive) {
      subscribers.set(onChange, keepAlive);
      updateInterval();
      return () => {
        subscribers.delete(onChange);
        updateInterval();
      };
    },
    now() {
      if (startTime === 0) {
        startTime = Date.now();